How to check for “Codes” on a 1990-1995 Mazda MX-5 Miata.

This video shows you how to check for diagnostic trouble codes / engine fault codes on pre-OBD2 Mazda MX-5 Miata and Eunos Roadster (1990-1995).

If your Miata has a code stored in its ECU / Engine Control Unit / Computer, the engine light or “MIL” Malfunction Indicator Light will flash.

For single digit codes: It will flash quickly. The number of flashes is your code number.

For two digit codes: It will flash and stay on for aprox 2 seconds, followed by a series of quick flashes.

Here is what the flash codes mean:

1990-1993:
1 Ignition pulse (no igf signal).
2 No Ne signal.
3 No G signal.
8 Airflow meter.
9 Water thermistor / coolant temperature sensor. .
10 Intake air thermistor in airflow meter.
12 Throttle position sensor open or short circuit.
14 Atmospheric pressure sensor (inside the ECU).
15 Oxygen sensor.
17 Oxygen sensor.
26 Purge solenoid valve (Evap canister purge valve).
35 ISC valve.

1994-1995:
1 IGF signal.
3 SGT signal.
4 SGC signal.
8 Mass airflow sensor.
9 Coolant temp sensor.
10 Intake air temp sensor.
12 Throttle position sensor.
14 Atmospheric pressure sensor (inside the ECU).
15 Oxygen sensor.
16 EGR function sensor.
17 Oxygen sensor.
25 PRC solenoid valve.
26 Purge solenoid valve (Evap canister purge valve).
28 EGR solenoid valve (vacuum).
29 EGR solenoid valve (vent).
34 ISC valve.

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Disclaimer:
Due to factors beyond the control of MiataMan, I cannot guarantee against improper use or unauthorized modifications of this information. MiataMan assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. Use this information at your own risk. MiataMan recommends safe practices when working on vehicles and or with tools seen or implied in this video. Due to factors beyond the control of MiataMan, no information contained in this video shall create any expressed or implied warranty or guarantee of any particular result. Any injury, damage, or loss that may result from improper use of these tools, equipment, or from the information contained in this video is the sole responsibility of the user and not MiataMan.